Friction between objects of different molecular structures creates static electric charges. This problem is particularly acute in the textile industry where certain textile processing operations require frictional contact between a yarn and various mechanical devices. Depending upon the nature of the yarn, positive or negative charges build up and often lead to deleterious consequences. A safe, economical means of controlling both positive and negative static electricity is, therefore, of considerable interest to the textile industry.
Many attempts have been made in the past to neutralize static electricity. One of the approaches commmonly employed involves Corona discharge electrostatic devices and another employs chemical additives, which are introduced into air-wash devices used in textile plants. Corona discharge devices suffer from their inability to produce long-lived charges on the particles they depend upon. Most anti-static formulations marketed for use in air-washers suffer from a lack of flexibility in that they are only able to solve half the problem existing in the control of static electricity; that is to say, they are capable of neutralizing either positive or negative static charges, but not both.
U.S. Pat. No. 3,924,157 and U.S. Pat. No. 4,077,914, to Peters and McAmish and assigned to the same assignee of the present application each that an aqueous solution of borax and a surfactant can be sprayed into a gaseous stream to impart a net positive electrical charge to the stream. It would be ideal if a method capable of neutralizing both positive and negative static charges could be provided. Similarly, U.S. Pat. No. 3,939,080 and U.S. Pat. No. 3,984,731 teach that dodecylbenzyl triethyl ammonium chloride can be added to an air-washer that delivers a flow of air to a room in which static electricity is present. Only negative static charges on objects are neutralized to any great extent. Thus, dodecylbenzyl triethyl ammonium chloride operates in a manner similar to a mixture of borax and a surfactant in that each imparts a predominantly net positive charge to an air stream.
Other methods for imparting a charge to a gaseous atmosphere are also known in the art, but each has its unique limitations. For example, merely contacting a gaseous stream with a water spray has been found sufficient to impart an electrical charge to the stream, but mainly only a negative electrical charge.
In other cases, a high electrical potential is applied to a water spray before being contacted with the gaseous stream. This method has not proved entirely satisfactory because of the electrical energy requirements, the safety hazards involved and periodic equipment breakdowns. Still other methods involve the use of radioactive substances. These methods have not proved entirely satisfactory because of the cost of the radioactive materials, the hazards involved in handling such materials and the cost of the safeguards that must be provided.
Thus, there exists a need in the art for a process for discharging both positive and negative static build-up. The process should be of relatively low cost to operate, fairly simple and safe to use without the need for costly equipment. The process should ideally be suited for use with existing air-wash systems in textile plants.